In fields such as medical and pharmaceutical industries, and liquid crystal display apparatus or semiconductor device manufacturing industries, harmful bacteria, impurity particles or particulate matters have a significant impact on product quality. Therefore, it becomes very important for the quality of a product whether the cleanliness meets a preset standard. In order to ensure the cleanliness of a clean room, it is particularly important to accurately grasp the airflow distribution characteristics in the clean room. Visual testing of clean airflow is one of the most effective methods for accurately grasping air distribution characteristics of a clean room. As shown in FIG. 1, at present, organic solvent is mainly used within a smoke-and-fog supplier, and also there is a case of using water vapor. Organic solvent can be used to make smoke-generation gas particles smaller and droplets smaller and more uniform, and incur a relatively increased amount of fog-generation and good density uniformity. With the characteristics of an gaseous state of an organic solvent and water vapor showing white or other colors in the air, the movement of the organic solvent gas-flow in the clean room can be observed, and therefore the airflow distribution situation in a clean room can be tested, thereby observing whether there is a phenomenon such as a hazardous vortex or an abnormal circulation, etc.